1. Field
The following description relates to a concurrent dual-band signal amplifier for use in a multi-band radio frequency (RF) receiving terminal. The concurrent dual-band amplifier has an inverted topology with a structure of stacked common sources.
2. Description of Related Art
Generally, in accordance with an increase in a demand for and diversification of standards for wireless communications, demand for a multi-band transmitter/receiver allowing a single portable device to simultaneously process signals within several bands has increased.
For example, in the case of wireless local area network (WLAN) usage, the 2.4 GHz and 5 GHz bands are being used simultaneously, and in the case of long term evolution (LTE) in Korea, the 800 MHz, 900 MHz, 1800 MHz, and 2.1 GHz bands are being used simultaneously.
Therefore, a device that is able to transmit and receive signals within multiple bands is desirable for use in a single radio frequency (RF) front end module. More specifically, a technology for processing signals at several frequencies or within a wide band of frequencies using a single low noise amplifier (LNA) positioned at an initial stage of a receiver is desirable.
Meanwhile, a low noise amplifier that supports a concurrent dual-band processor that is able to simultaneously process signals within two different bands and is able to support a wide band of frequencies may have a cascode structure or a cascade structure. For example, a cascode structure is a structure using a two-stage amplifier composed of a transconductance amplifier followed by a current buffer. By contrast, a cascade structure is an amplifier that has a two-port network constructed from a series of amplifiers, where each amplifier sends its output to the input of the next amplifier in a daisy chain.
Thus, an amplifier having such a cascode structure has a structure in which two transistors are stacked between a power terminal and a ground terminal (GND) and has a single current path, such that only a small amount of current is consumed. However, since an amplifier having a cascode structure includes a common gate amplifier whose gain characteristics may be poor and a common source amplifier whose gain characteristics may be excellent, in such a case corresponding to using the common gate amplifier, it is desirable to improve gain characteristics.
Also, in further detail, an amplifier that has a cascade structure has a structure in which amplifying units of at least four stages are located between an input terminal and an output terminal, and the amplifying units of respective stages are formed using a common source amplifier, such that gain characteristics of such amplifying units are excellent. However, because a large amount of current may be consumed when such a cascade structure is used due to the presence of two or more current paths, it is desirable for the amplifier having such a cascade structure to be improved in terms of current consumption.
As described further above, in the case of using the common source amplifier for which gain characteristics are excellent, an issue that a relatively large amount of current is consumed presents itself.
Alternative approaches disclose use of a dual-band low noise amplifier, but do not disclose a solution for the previously mentioned issue related to simultaneously achieving good gain characteristics while consuming a moderate amount of current.